Merge pull request #57 from boolean-uk/41-api-create-new-cohort-and-get-a-cohort-by-id

41 api create new cohort 

Looking good

Author: johanreitan

exercise.wwwapi/DTOs/Cohorts/CohortDTO.cs

@@ -0,0 +1,18 @@
+
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+using System.Text.Json.Serialization;
+
+namespace exercise.wwwapi.Models;
+
+public class CohortDTO
+{
+    [JsonPropertyName("course_id")]
+
+    public int CohortNumber { get; set; }
+
+    public string CohortName { get; set; }
+
+    public DateTime StartDate { get; set; }
+    public DateTime EndDate { get; set; }
+}

exercise.wwwapi/DTOs/Cohorts/CohortPostDTO.cs

@@ -0,0 +1,10 @@
+
+using System.Text.Json.Serialization;
+
+public class CohortPostDTO
+{
+    public string CohortName { get; set; }
+
+    public DateTime StartDate { get; set; }
+    public DateTime EndDate { get; set; }
+}

exercise.wwwapi/Data/ModelSeeder.cs

@@ -255,7 +255,6 @@ private static void SeedCohorts(ref ModelBuilder modelBuilder)
                 EndDate = new DateTime(2026, 3, 29),
             }
 
-
         );
     }
 
@@ -306,8 +305,6 @@ private static void SeedUserCC(ref ModelBuilder modelBuilder)
                 CcId = 1,
                 UserId = 3
             }
-
-
         );
     }
 

exercise.wwwapi/Endpoints/CohortEndpoints.cs

@@ -1,4 +1,10 @@
-using Microsoft.AspNetCore.Mvc;
+using exercise.wwwapi.DTOs;
+using exercise.wwwapi.Enums;
+using exercise.wwwapi.Models;
+using exercise.wwwapi.Repository;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using Npgsql;
 
 namespace exercise.wwwapi.Endpoints;
 
@@ -9,9 +15,57 @@ public static void ConfigureCohortEndpoints(this WebApplication app)
         var cohorts = app.MapGroup("cohorts");
         cohorts.MapPost("/", CreateCohort).WithSummary("Create a cohort");
     }
-    [ProducesResponseType(StatusCodes.Status200OK)]
-    public static async Task<IResult> CreateCohort()
+    [ProducesResponseType(StatusCodes.Status201Created)]
+    [ProducesResponseType(StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(StatusCodes.Status500InternalServerError)]
+    public static async Task<IResult> CreateCohort(IRepository<Cohort> cohortRepo, CohortPostDTO? postCohort)
     {
-        return TypedResults.Ok();
+        if (postCohort == null || postCohort.StartDate == DateTime.MinValue || postCohort.EndDate == DateTime.MinValue)
+        {
+            return TypedResults.BadRequest("Missing cohort data");
+        }
+
+        bool success = false;
+        int attempts = 0;
+        int newCohortNumber = 0;
+
+        while (!success && attempts < 5)
+        {
+            try
+            {
+                var maxCohortNumber = (int?) await cohortRepo.GetMaxValueAsync(c => c.CohortNumber);
+                if (maxCohortNumber == null)
+                {
+                    maxCohortNumber = 0;
+                }
+                if (postCohort.CohortName == null)
+                {
+                    postCohort.CohortName = $"Cohort {maxCohortNumber + 1}";
+                }
+
+                newCohortNumber = (int)(maxCohortNumber + 1);
+                Cohort newCohort = new Cohort { CohortNumber = newCohortNumber, CohortName = postCohort.CohortName, StartDate = postCohort.StartDate, EndDate = postCohort.EndDate };
+
+                cohortRepo.Insert(newCohort);
+                await cohortRepo.SaveAsync();
+                success = true;
+            }
+            catch (DbUpdateException ex) 
+            {
+                if (ex.InnerException is PostgresException CohortNumberEx &&
+                     CohortNumberEx.SqlState == "23505") //23505 = Cohort number value already exists
+                {
+                    attempts++;
+                }
+                else
+                {
+                    Console.WriteLine($"DB update error: {ex.StackTrace}");
+                    return TypedResults.InternalServerError($"Error while updating the database: {ex.Message}");
+                }
+            }
+        }
+
+        return TypedResults.Created($"/cohorts/{newCohortNumber}");
     }
+
 }

exercise.wwwapi/Endpoints/UserEndpoints.cs

@@ -428,4 +428,4 @@ private static bool AuthorizeStudent(ClaimsPrincipal claims)
 
         return false;
     }
-}
+}

exercise.wwwapi/Repository/IRepository.cs

@@ -20,4 +20,5 @@ public interface IRepository<T>
     void Delete(T obj);
     void Save();
     Task SaveAsync();
+    Task<object> GetMaxValueAsync(Expression<Func<T, object>> columnSelection);
 }

exercise.wwwapi/Repository/Repository.cs

@@ -1,6 +1,8 @@
 using exercise.wwwapi.Data;
 using Microsoft.EntityFrameworkCore;
 using System.Linq.Expressions;
+using System.Numerics;
+using System.Reflection.Metadata.Ecma335;
 
 namespace exercise.wwwapi.Repository;
 
@@ -45,7 +47,7 @@ public async Task<IEnumerable<T>> GetAllAsync(params Expression<Func<T, object>>
 
         return await _table.ToListAsync();
     }
-    
+
     public T? GetById(object id, params Expression<Func<T, object>>[] includeExpressions)
     {
         if (includeExpressions.Length != 0)
@@ -81,7 +83,8 @@ public async Task<IEnumerable<T>> GetAllAsync(params Expression<Func<T, object>>
             return await query.FirstOrDefaultAsync(e => EF.Property<object>(e, "Id").Equals(id));
         }
 
-        return await _table.FindAsync(id);    }
+        return await _table.FindAsync(id);
+    }
 
     public void Insert(T obj)
     {
@@ -127,4 +130,9 @@ public async Task<T> GetByIdWithIncludes(Func<IQueryable<T>, IQueryable<T>>? inc
         var res = await query.Where(a => a.Id == id).FirstOrDefaultAsync();
         return res;
     }
+
+    public Task<object> GetMaxValueAsync(Expression<Func<T, object>> columnSelection)
+    {
+        return _table.MaxAsync(columnSelection);
+    }
 }

exercise.wwwapi/appsettings.json

@@ -13,4 +13,4 @@
   "ConnectionStrings": {
     "DefaultConnection": "Host=${Neon:Host}; Database=${Neon:Database}; Username=${Neon:Username}; Password=${Neon:Password}; SSL Mode=VerifyFull; Channel Binding=Require;"
   }
-} 
+}